Formula parameterization in CATIA V5 – beginner tutorial

It is my first CATIA Tutorial about parameterization in CATIA V5 using Formula command. It is simple and very useful when you want to create a single part with possibility to change fast multiple dimension and features.

With this command and with some knowledge about engineering you can create, for example, multiple parts from same family, like screws, washers or nuts. You must know a formula to do that. For example, for washers, you must know the difference between interior and exterior diameter that is 1/2 or other value and the thickness is 1 mm for all washers that have the exterior diameter smaller than 15 mm or something like this. I think you got the idea.

In this tutorial I want to show you how to use CATIA to do that, and after that you will be able to create by own any family of parts.

The beginning of Formula utilization

We have a dedicated module for Formula, relations and more, and it is called Knowledge Advisor. You can access the formula command also from Part Design Module and also from Generative Shape Design by pressing f(x) icon from Knowledgetoolbar.

How to do any washer using parameterization

1. You must create a part using simple features without sketches. For my washer I created 2 circles, one with Dext=20 mm and another with Dint=10 mm. I use Pad command to extrude first circle and Pocket command to make the interior hole for the washer.

2. After that I want to change the interior and exterior diameter manually using Parameters. To do that you must press the Formula command. To be easier, select from Filter Type -> User parameters (to list all Parameters created by me). Now, click on New Parameter of type button and create 3 new parameters: Thickness, Interior Diameter, and Exterior Diameter.

3. In the previous step I created 3 parameters. Now I must associate these parameters with washer dimensions.

Thickness parameter – now you must associate each parameter to one existing dimension. We need to find now Pad size, Interior radius and Exterior radius. To do that, click again on formula f(x) and the window that appeared select Filter Type to Length and find the dimensions that you want to associate, in my case:

‘Geometrical Set.1\Circle.1\Radius’ => ‘Interior diameter’ (Pocket.1)

‘Geometrical Set.1\Circle.2\Radius’ => ‘Exterior diameter’ (Pad.2)

‘PartBody\Pad.2\FirstLimit\Length’ => ‘Thickness’ (Pad.2 length)

To do that, double click on ‘Geometrical Set.1\Circle.1\Radius’ and in the new window that appeared you should find in Members of Length ‘Interior diameter’ and select it using double click.

If you select any Member of Length you will see the value of that dimension. In my case, if I select the ‘Geometrical Set.1\Circle.1\Radius’ I’ll see 10mm, if I select ‘Geometrical Set.1\Circle.2\Radius’ I’ll see 20mm.

Do same for other 2 parameters, Exterior diameter and Thickness.

Parameterization is very useful when you want to use a type of part with different dimensions, like screws, nuts or washers.

Tip: To find much faster a parameter, I suggest to rename all Pads or other elements with other names more easy to finding parts. To do that, select Pad, right click on it and select Proprieties (ALT+ENTER) and go to tab Feature Proprieties and in the Feature Name box use another name for selected element.

Note: It’s very important to put the measure unit for constant parameters. For example, if you want to have the diameter of a circle 20 mm you must tell to Formula box that. So, in formula editor you must put 20 mm not only 20.

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Comments

Hi,
I have been using formulas and equivalent dimensions a lot. However, there is something I have not managed to crack.

Sometimes formulas, eq dims etc knowledge based stuff get disabled. Icons are grayed out. This happens every now and then without any clear reason to me.

Any idea what’s going on? I’m in the middle of a very laborious modeling and my eq dims have disappeared and knowledge based stuff is disabled. Has it something to do with copy and paste the profile I’m having the eq dims? Quick reply is much appreciated,

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